Choke type shorting plunger



1962 F. E. vAccARo ETAL 3,049,684

CHOKE TYPE SHORTING PLUNGER Filed Feb. 13, 1 961 Fig. 4

R 5 m M m m M, I. A M R 9 K W mm Y B United States hatent 3,049,684 CHOKE TYPE SHORTING PLUNGER Frank E. Vaccaro, New Brunswick, N.J., and Frank R.

Arams, Forest Hills, N.Y., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Feb. 13, 1961, Ser. No. 89,082 6 Claims. (Cl. 333-98) The present invention relates to a choke-type shorting plunger and, more particularly, to such a shorting plunger used to produce a variable short in a ridge-type waveguide.

Choke-type shorting plungers, because they are noncontacting, present an advantage over contact shorting plungers. in contact shorting plungers there is always the problem of ensuring maintenance of satisfactory contact between the plunger and the waveguide it shorts. Failure to maintain satisfactory shorting contact between the waveguide and the contact shorting plunger is particularly disadvantageous in high-power applications. Contact shorting plungers which are called upon to ensure an intimate contacting action generally rely upon spring action to accomplish this result. The reliability of this spring action for ensuring satisfactory contact is not great and diminishes as the spring resiliency shifts with age. In addition, the spring action usually causes wear in the contacting portions of the plunger and guide yielding even further detrimental effects.

The present invention comprises a non-contacting choke-type shorting plunger for use with a ridge-type waveguide to form such structures as a magnetron tuning cavity or a waveguide transmission line designed to transmit very wide ranges of frequencies. The non-contacting choke portion of the plunger is mechanically supported within the ridge-type waveguide by a plunger guide for controllable longitudinal movement along the waveguide and is of extremely simple construction, clearing the opposing ridges of the waveguide by a very small clearance to maximize shorting action and effectively blocking the electromagnetic field in the waveguide by extending but a small portion above and below the upper and lower ends, respectively, of the opposed Waveguide ridges. The plunger guide, whose face is at an optimum electrical distance (approximately 7t/ 4) from the face of the choke portion so as to produce a reflected short at the longitudinal position, within the waveguide, of the face of the choke portion, physically closes off the back of the tuning cavity or transmission line (as the Waveguide may be) and rides slidably within the waveguide so as to clear the opposing faces of the opposed waveguide ridges by a small clearance with the combined result of preventing power loss within the operative part of the Waveguide by blocking the loss of any energy that gets coupled past the plunger choke portion and ensuring prevention of wear to the opposing faces of the opposed waveguide ridges. A flexible interconnector linking the plunger guide and the rearwardly disposed operator-controllable actuating mechanism for selectively positioning the choke portion face at the desired longitudinal position within the Waveguide ensures that any misalignment in the actuating mechanism is not transmitted to the choke portion to cause it to touch the waveguide.

An object of the present invention is the provision in a waveguide of a variable short which combines a highly efficient shorting action with a high degree of reliability.

Another object is to provide a choke type shorting plunger for use with ridge-type waveguides.

A further object is to provide a choke type shorting plunger yielding a minimum of wear on the effective waveguide boundaries.

' Still another object is to provide a choke type shorting plunger protected from undesirable contact action with its waveguide through fault of any misalignment in its actuating mechanism.

An additional object is provision for use with ridgetype waveguides of a choke type shorting plunger of very simple construction.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which like reference numetals designate like parts throughout the figures thereof and wherein:

FIG. 1 shows a partially cut away perspective view of the choke-type shorting plunger located within its ridgetype waveguide;

FIG. 2 shows in perspective the forward portion of the choke type shorting plunger;

FIG. 3 is an end view, as seen from the left-hand end of FIG. 1, of the shorting plunger and the ridge-type waveguide; and

FIG. 4 shows a horizontal view, partly in section, of the shorting plunger mechanism and the Waveguide within which it is positioned.

Referring now to the drawing, wherein like reference numerals designate corresponding parts throughout the several views, FIG. 1 shows, in perspective, a section 11 of a ridge-type waveguide such as would be found in a magnetron tuning cavity or in a waveguide transmission line. Running longitudinally along the inner surface of waveguide 11 are waveguide ridges 12 diametrically opposed to one another and presenting to each other parallel innermost surfaces.

Disposed within ridge-type waveguide section 11 is a choke-type shorting plunger 13 which consists of a choke 19, plunger guidesections 14 and 16, and a flexible connector 2.6 connecting these elements to a rearwardly-disposed plunger actuating member, later to be described in detail. Plunger guide forward section 14 slidably mates with the inner surface of waveguide section 11 and fixedly supports non-contacting choke 1'9. Plunger guide after sections 14 and 1 6, respectively, are formed with longitudinally-disposed slots 17 at diametrically opposite portions thereof so that plunger guide sections 14 and 16 may ride freely along the longitudinal axis of waveguide 11, the slots 17 in plunger guide sections 14 and 16 having a cross-sectional shape complementary to that of waveguide ridges 12 and permitting plunger guide 1416- to clear the ridges 12 by a small clearance, as best seen in FIG. 3. Plunger guide after section 16 terminates in a stop member 18 which does not clear ridges 12 but comes to an abutting stop against ridges 12 when choke-type shorting plunger 13 reaches the desired limit of its inboard movement into the operative portion of waveguide section 11. Illustrative of the use of plunger stop member 18 are such purposes as ensuring that choke 19 cannot penetrate far enough into a transmission line so as to touch and distort a magnetron to tuning cavity iris, when such is present, or to penetrate too far into the magnetron resonator to which the tuning cavity is coupled.

Connected to plunger guide after section 16 by a flexible connector 26 is an operator-actuated portion of shorting plunger 13 consisting of a cylindrically shaped plunger block 27 fixedly mounted to an inner sleeve 29 which has secured to its outermost end a bellows ring 311 Plunger block 27 and its sleeve 29 mate with the cylindrically shaped inner portion (having no ridges) of wave.- guide section 11 for sliding, longitudinally-translatory movement therein in response to any sort of conventional control for translatingly moving the shorting plunger such as a micrometer or any other external control device adapted to pass through bellows ring 31' and connect to plunger block 27 by means of the threaded tap 28. Connector 26 is sufliciently flexible to preclude transmission to plunger guide 14--16 of any misalignment from the actuating mechanism 27-=29-3'1 and is at the same time sufficiently rigid to enable accurate control of the translatory movement of the choke-bearing plunger guide 1'41-6 by the actuating mechanism 27--2931.

Non-contacting choke 19 is of a simple T-shaped construction having a forward face 21 and side faces 22 and 23 respectively. Forward face 21 runs transverse to the longitudinal axis of waveguide section 11 and side faces 23 and 22 extend parallel to the longitudinal axis of waveguide section 11 to within close proximity to the transversely extending forward face 15 of plunger guide forward section 14. Faces 22, 2B of choke 19 run parallel to the inboard opposed faces of ridges 12 and are separated therefrom by a small clearance. Forward face 21 of choke 19 which is coincident in height with side faces 22, 23 clears the ridges 12 by a small clearance and extends in height somewhat below and above ridges 12 to block off the great bulk of the electromagnetic energy passing down the waveguide between ridges 12. The slight extension of the choke 19 above and below ridges L2 ensures the blockage of peripheral electromagnetic energy which fans out a bit at the upper and lower limits of the opposed ridges 12. The small amount of energy that does get coupled past the choke 19 is reflected back from the cavity formed behind face 21 by faces 22 and 23 and from the transversely-extending face 15 of plunger forward guide section 14 to present a reflected short at choke face 21 because of the substantially 4 spacing between choke face 21 and plunger guide forward section face 15, 7\ being the wavelength for the operating frequency at which the waveguide is being operated. Accordingly, the short at face 21 is effectively maximum. .The invention contemplates different sized chokes 19 to acommodate the shorting plunger to various frequencies. Choke blade 24 can be made removeable from plunger guide forward portion 14 to enable substitution of dilferent size chokes 19 as different 4 spacings between choke face 21 and plunger guide forward section face 15 are required.

By varying the longitudinal position of face 19 within the ridged portion of waveguide section 11 a highly effective shorting action thus can be operator controlled for producing variable tuning for resonator or transmission purposes at selected frequencies. This shorting action is further marked by a high degree of reliability and a minimum of wear on the controlling parts of the device.

It should be understood of course that the foregoing disclosure relates only to an exemplary embodiment and that it is intended to cover all changes and modifications which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. The combination of a ridge-type waveguide having a pair of opposed ridges disposed on opposite internal portions thereof and running longitudinally for a substantial distance along said waveguide and a choke-type shorting plunger means slidably mounted said waveguide so as to be translatingly shiftable along the longitudinal axis of said waveguide for producing a movable short circuit in the rigid portion of said waveguide wherein said choke-type shorting plunger means comprises a choke means interposed between said ridges for substantially short circuiting. said ridges without making physical contact therewith; a joint reflecting and supporting-andguiding means connected to said choke means and slidably mounted in said waveguide for sliding translatory movement along the longitudinal axis of said waveguide, including along the ridged portion thereof, for performing the dual functions of reflecting any electromagnetic energy which gets past said choke means as a short at the operative shorting location of said choke means and of fixedly supporting said choke means in operative shorting position between said waveguide ridges and guiding 4 said choke means for longitudinal travel along the ridged portion of said waveguide; operator-controllable control means slidably mounted in the unridged portion of said waveguide for controlling the longitudinal positioning of said choke means and said joint reflecting and supportingand-guiding means in said waveguide; and flexible connector means interconnecting said reflecting and supporting-and-guiding means and said control means for imparting to said reflecting and supporting-and-guiding means and to said choke means the operator-controllable translatory movement of said control means, said imparted translation being free of any misalignment in said control means.

2. The combination of a ridge-type waveguide having a pair of opposed ridges disposed on opposite internal portions thereof and running longitudinally for a substantial distance along said waveguide and a choke-type shorting plunger means slidably mounted within said waveguide so as to be translatingly shiftable along the longitudinal axis of said waveguide for producing a movable short circuit in the ridged portion of said waveguide wherein said choke-type shorting plunger means comprises a slotted guiding member slidably mounted within said waveguide for translatory movement along the longitudinal axis of said waveguide and susceptible of translatory movement along both the ridged and unridged length of said waveguide, a choke means fixedly carried by said guiding member and interposed between the opposed ridges of said waveguide for short circuiting said ridges without making physical contact therewith an operator-controllable actuating means connected to said guiding member for controlling the longitudinal positioning of said choke means within the ridged portion of said waveguide, said guiding member comprising a forward portion connected to said choke means and an after portion connected to said actuating means, the forward portion of said guiding member constituting a longitudinally-slotted plug which presents to said choke means a planar face transverse to the longitudinal axis of said waveguide, said planar face having an outer periphery matingly complementary to a cross section taken through the rigid portion of said waveguide along a plane transverse to the longitudinal axis thereof so as to constitute a reflecting barrier which closes ofl the escape route ofany electromagnetic energy which gets past said choke means, said plug further having a longitudinally-extending peripheral surface matingly slidable along the ridged portion of said waveguide, the longitudinal slots in said plug enabling said plug to slide freely along the ridges of said waveguide, and the after portion of said guiding member having transverse dimensions less than those of said plug so as to be out of contact with the inner surface of said waveguide and having longitudinally extending slots therein in alignment with the slots in said plug, said after portion slots extending almost the entire length of the after portion to allow translation of the after portion of said guiding member along the ridged portion of said waveguide, said after portion being further defined by a stop section at its end connected to said actuating means, said stop section extending outwardly from the longitudinal axis of said waveguide to come into abutting contact with the end of the waveguide ridges thereby limiting the inward path of travel into said waveguide of said guiding member and'the choke means carried thereby.

3. The combination of claim 2 wherein said choke means comprises a member substantially T-shaped in cross section and wherein the parallel depending sides of the T are almost as long as the central portion thereof and all portions of the T-shaped member are of coincident height in the direction normal to said cross section, the depending parallel sides of said T-shaped member being rectangularly shaped and running parallel to the opposing faces of the respective ridges with small clearance therefrom and the top portion of said T presenting a planar face having sides each of which is complementary in shape to the cross-sectional shape of the adjacent opposing face of the adjacent waveguide ridge and a top and a bottom extending somewhat above and below the tops and bottoms respectively of the opposed ridges, said choke means being secured to said plug such that the central portion of said T-shaped member lies along the longitudinal axis of said waveguide, the distance between the planar face of the top portion of said T and the planar face of said plug being substantially a distance of M4, A being the wavelength for the particular operating frequency of the waveguide.

4. A choke-type shorting plunger for use with a ridgetype waveguide having opposed ridges disposed on opposite internal portions thereof and running for a substantial distance along the longitudinal length of said waveguide comprising a substantially-T-shaped choke means adapted to short the opposed ridges of said waveguide without making physical contact with said ridges, a longitudinally-slotted guiding member supportingly mounted to said choke means and adapted to ride translatingly along the longitudinal axis of said waveguide in both the ridged and unridged portions thereof, said guiding member having a forward planar face disposed transverse to the longitudinal axis of said plunger means and adapted, when said plunger means is in operative registry with said ridgetype waveguide, to physically block loss past said guiding member of any leakage electro-magnetic energy which gets coupled past said choke means, the planar face of said guiding member having a peripheral conformation formed to cornplementarily mate with the transverse-section internal shape of the ridged portion of the particular waveguide being employed and said planar face during its travel along said Waveguide being adapted to being oriented transverse to the longitudinal axis of said Waveguide, said guiding member having a bearing portion whose longitudinally-extending periphery has a transversely-defined shape coincident with that of the planar face of said guiding member to permit easy translation of said guiding member along the longitudinal axis of said waveguide, the transverse shapes of the planar face of said guiding member and of the bearing portion of said guiding member having slots defined therein to allow said guiding member to ride freely along the ridged portion of said waveguide, and operator-controllable actuating means connected to said guiding member for controlling the longitudinal positioning of said choke means within the ridged portion of said waveguide.

5. The choke-type shorting plunger of claim 4 wherein said T-shaped choke means presents a planar face at the top of the T which is parallel to the planar face of said guiding member and is separated therefrom by a distance of substantially A/ 4, A being the wavelength of the operating frequency for which the waveguide is being shorted.

6. The choke-type shoring plunger of claim 5 wherein the T-top planar face of said T-shaped choke means has sides complementary in shape to the respective opposing faces of the opposed waveguide ridges, said sides being adapted respectively to clear by a small dimension the opposing faces of the opposed ridges when said shorting plunger is in operative position in said waveguide and to extend slightly above and below said ridges during said operative position.

References Cited in the file of this patent UNITED STATES PATENTS 2,677,111 Stahl Aug. 27, 1954 2,758,287 Jacobsen Aug. 7, 1956 2,829,352 Hennies Apr. 1, 1958 2,850,705 Chait Sept. 2, 1958 

